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3. SPEClFlCATlONS
MELSEC-A
3.2.3
US-422 terminal
block specifications
Signal
Signal Direction
AJ71 C24
-
Abbreviation
Computer
Description
I
sDA
I
I
Send data
I
Send data
Receive data
Receive data
Signal ground
I
FG
I
I
Frame ground
I
Fig. 3.2 RS-422 Terminal Block Specifications
(1)
Fig. 3.3 shows the RS-422 function block
diagram.
I
Transmit data
sDA
SDB
h
U
-
k2
Receive data
1
RDA
330
RDB
'
. l : S e c 4 3 . 2 SW23
p . p . p . p . p . p . p .
- 2 : Sec. 4 . 3 . 2 SW24
Fig. 3.3 RS-422 Function Block Diagram
3.2.4 US-422 cable specifications
An
R S - 4 2 2
cable is recommended in Section
3.2.1. Other
types
o f
cables
may be used instead,
if
they
c o n f o r m
to the specifications
listed in the
f o l l o w i n g
table.
Item
I
Insulation resistance
1
10.000 MR km or less
I
Description
Number of pairs
Cable tvve
I
Shielded cable
3 Pairs
Conductor resistance 120•‹C)
1
88.0 R/km or less
Dielectric strength
500 VDC, 1 minute
Characteristic impedance (100
KHz)
Electrostatic capacity (1 KHz)
I
60 nF/km or less on average
110
+.
10 R
I
Fig. 3.4 RS-422
Cable Specifications
(km
= 0.621
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